As shown in FIG. 9, an existing MMW (Micro and Millimeter Waves, micro and millimeter waves) circuit includes a circuit board (for example, a PCB). The circuit board is placed on a heat substrate (a metal block with heat conductivity, such as a copper block or an aluminum block). The circuit board is opened with a window. A bare chip is placed in the window, and placed on the heat substrate.
The bare chip is adhered on the heat substrate through electrical conduction materials such as silver paste, so that good heat conduction and electrical conduction connection exists between the bare chip and the heat substrate. The bare chip is electrically connected to a conductor layer on a surface of the circuit board through a bonding wire. In this structure, reference ground of the bare chip, the bonding wire, and a micro-strip line that is placed on the circuit board are all the heat substrate.
The circuit board adopted in the existing MMW circuit is only disposed with one layer of conductors, so large-scale circuit design cannot be implemented.